1. Technical Field
The present invention relates to a test apparatus, a shift amount measuring apparatus, a shift amount measuring method and a diagnostic method. More particularly, the present invention relates to a test apparatus for testing a device under test, a shift amount measuring apparatus and a shift amount measuring method for measuring a phase shift amount of a signal under measurement, and a diagnostic method for a test apparatus.
2. Related Art
A test apparatus generates an edge timing by delaying a reference clock, and outputs a test signal the level of which varies at the generated edge timing to a device under test. The test apparatus receives an output signal output from the device under test in response to the test signal, at a timing indicated by a strobe signal, and judges whether the device under test passes or fails the test by comparing the received output signal with an expected value signal. Also, the test apparatus measures an actual phase shift amount of the test signal, for example, at regular time intervals, in order to diagnose whether a PLL or the like provided in the test apparatus is broken. A test apparatus is disclosed which tests a device under test that has a high-speed serial interface of clock-embedded type in, for example, Unexamined Japanese Patent Application Publication No. 2005-285160.
Here, in the conventional art, when measuring the phase shift amount of the test signal, the test apparatus retrieves the test signal at each timing of the strobe signal that is scanned in the temporal direction, to detect the edge timing of the test signal. Scanning the strobe signal in the temporal direction, however, such a conventional test apparatus requires a complex operation.